青海祁连山冻土区发现天然气水合物

Gas Hydrates in the Qilian Mountain Permafrost,Qinghai,Northwest China

祁连山冻土区位于青藏高原北缘,多年冻土面积约10×104km2,具有良好的天然气水合物形成条件和找矿前景。2008～2009年间中国地质调查局在青海省天峻县木里煤田聚乎更矿区施工"祁连山冻土区天然气水合物科学钻探工程",迄今共完成钻探试验井4口,总进尺2059.13m,分别在DK-1、DK-2和DK-3钻井中钻获天然气水合物实物样品,取得了找矿工作的重大突破。天然气水合物产于冻土层之下,埋深133～396m。水合物呈白色、乳白色晶体,点火能燃烧,红外热像仪测温后呈明显的低温异常,放进水里强烈冒泡,水合物分解后能不断冒出气泡和水滴,并残留下特征的蜂窝状构造。激光拉曼光谱仪检测呈现特征的水合物光谱曲线,测井曲线也具有较明显的高电阻率和高波速标志。祁连山天然气水合物具有冻土层薄、埋深浅、气体组分复杂、以煤层气成因为主等明显特征,是一种新类型水合物。这是我国冻土区首次钻获的天然气水合物实物样品,也是全球首次在中低纬度高山冻土区发现天然气水合物实物样品,具有重要的科学意义和经济意义。

Qilian Mountain permafrost, with an area of about 10×10^4 km^2 , is located in the north of Qinghai- Tibet plateau. It has of perfect conditions and great prospecting potential for gas hydrate. The Scientific Drilling Project of Gas Hydrate in the Qilian Mountain permafrost, which locates at the Jugenghu Mining Area in the Mull Coalfield, Tianjun County, Qinghai Province, has been implemented by China Geological Survey in 2008-2009. Four scientific drilling wells have been completed with a total footage of 2059.13m. Samples of gas hydrate were collected separately in the holes of DK-1, DK-2 and DK-3. Gas hydrate is hosted under permafrost zone at the 133-396m interval. The samples are white or ivory crystal and easily burning. Distinct low temperature anomaly has been identified by infrared camera. The gas hydratebearing cores strongly bubble in water. Gas-bubble and water-drop emit from the samples and then retain characteristic honeycombed structure. The typical spectrum curve of gas hydrate is detected using Raman spectrometry. Furthermore, the logging profile also indicates high electrical resistivity and sonic velocity. Gas hydrate in Qilian Mountain is found within a thinner permafrost zone with a shallower buried depth and characterized by more complex gas component and coalbed methane origin, suggesting a new type of hydrate.